import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class Demo3 {
    private static int sum = 0;
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        Callable<Integer> callable = new Callable<Integer>() {
            @Override
            public Integer call() throws Exception {
                for (int i = 0; i < 1000; i++) {
                    sum++;
                }
                return sum;
            }
        };

        FutureTask<Integer> futureTask = new FutureTask<>(callable);

        Thread t = new Thread(futureTask);

        t.start();
        t.join();

        System.out.println("sum = " + futureTask.get());
    }
}
